Replies to This Discussion

Permalink Reply by Wes "I'm Baaaaack" Yates on September 11, 2011 at 4:27am

Check the scale and also check the nut height (String height at nut). Sounds like your strings are making the notes sharp closer to the nut and thus you flatten the tuning (perhaps).

 

OR

 

Check the scale against StewMac, etc, to see if you indeed have the correct spacing.

 

Raising or lowering the bridge would affect the 12th fret but mostly when the 12th is sharp. I doubt that if the tuning is spot on, the 12th would be anything else but on assuming correct string height and fret location. Intonation can be the issue. Move the bridge back and forth. See if that works. BUT again, check the nut height. When you change the intonation you change the relative position of all the frets!

 

-WY

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Permalink Reply by Wes "I'm Baaaaack" Yates on September 11, 2011 at 4:40am

This is sorta how I see string tension versus fret position. Mind you, its not a GREAT deal of tension but could sharpren the notes closer to the nut by 50 cents (0.5 semitone). I (and others) reduce the nut-to-first distance by 1/32 +/- to compensate. This works REALLY well and I have had no issues doing this.

 

In the image above, I see more tension closer to the first few frets that at the 12th, where just about equal tension is present.Not completely accurate here but imagine at the first fret lets say there was a 2:1 tension ratio, but a 1:1 ratio at the 12th. That's more or less how I see it.

 

One oddity you may be asking is: So if you shorten the distance at the first, wouldn't that cause the note to be sharper based on even shorter distance and thus more tension? Well, yes, but also know that it does throw off all the frets distances -- especially the 12th, which i compensate for with intonation. It works. Keep in mind, string height at the nut affects the 1-5th frets even more so that does the shorter 1st distance.

 

Just my opinion but it seems to fall in line with what I see happening.

 

-WY

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Permalink Reply by Ron "Oily" Sprague on September 11, 2011 at 8:12am

Doug,

There are a number of checks you may need to make to find the actual source of the problem.

Wes' solution is compensation at the nut. This may cure the problem, but the fact that you say frets 1-11 seem to be in tune, while frets 12-20 are flat suggest several other possibilities to me. Please understand, I'm not saying Wes is wrong; he has waaaayyy more build experience than I do. I'm just offering alternatives in case his solution doesn't fix your problem.

One of your other statements seems to conflict with you saying that frets 12-20 are flat: you also say that when playing the scale "down" the fretboard, frets 1-20 seem fine.

Here's some other things to check:

1) Assuming you do not have a fixed bridge, try a) moving the bridge backward or forwards in small increments, and / or b) angling the bridge. Check the tuning of your lowest, heaviest string at each fret, using a digital or analogue tuner. If all seems well on that string, make the point at which the bridge works for that string the pivot point, then do the same procedure for your highest, lightest string. The bridge will make an angle across the strings; this results in crude compensation at the bridge, acting somewhat like individual string saddles to allow for a rough intonation solution.

2) Using a digital or analogue tuner, check the pitch of each string at each fret. Perhaps you have already done this, but I suggest it because of the two apparently inconsistent statements above: in tune for frets 1-11, flat from frets 12-20, but plays the scale in tune from frets 1-20. Is this true for all strings?

3) You don't mention what string gauges you are using, nor what tuning they are in. It is a possibility that you may be experiencing some neck bowing from the 12-20th frets. For some reason, I wonder if your short scale length and (perhaps?) too heavy string guage are causing this. This is a common problem on really cheap mass-produced guitars, and is often cured by a) adding a truss rod, b) incrementally changing the bridge height by shimming or using a shorter or taller bridge, c) changing string gauges, or d) some combination of these. Try string gauges, then bridge height first; you may hit on a combo that precludes you rebuilding the neck. That would be a last resort.

4) Have you checked your fret heights up and down the neck, using a metal straightedge? It is also possible frets 12-20 are at different heights than frets 1-11.

I'd try Wes' nut suggestion first, then look at bridge placement, then bridge angling, then bridge height, then string gauge, then fret height, before doing any serious neck rebuild.

It would also help if you could post pics before and after each step; one of us, or somebody else, may catch some detail that could help diagnose the problem further.

Let us know what works for you, as you will neither be the first nor the last to experience this problem. Your experience will undoubtedly help some other poor slob who gets addicted to building these things.

Good luck!

Oily

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Permalink Reply by Dan Sleep on September 11, 2011 at 8:24am

Wes and Oily have handed out some good advice. The only thing I would add is to do Oily's step 2 first, and using a digital tuner, confirm the actual values of the notes so you know exactly what you are dealing with.

 

And I am curious what you used to mark the fret spacing?

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Permalink Reply by Wes "I'm Baaaaack" Yates on September 11, 2011 at 9:05am

String gauge! yes. That would indeed be a possibility as well your question 'Is this true for all strings?'

 

-WY

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Permalink Reply by Outhouse Instruments on September 11, 2011 at 10:33am

With correct nut and bridge height and correct frets, string gauge should have no effect on tuning unless you have a mix of gauges. ( lights, mediums, heavies, etc.)

Wes is right about the fretting increasing tension and changing tuning. It's impossible to completely get rid of this without nut/bridge compensation or moving the frets around ...... really not recommended ( IMHO) for a newer builder.

The best thing is to work on your set-up. String height as low as possible without buzzing and the bridge adjusted for correct intonation.

Maybe for funnsies, grab another fret program and double check everything ..... I've always thought the Stew-Mac was a bit clumsy to use.

 

 

Matt

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Permalink Reply by Douglas Eric Marsalis on September 12, 2011 at 11:26pm

Thanks guys for all of your replies.  I will write some updates once I work on the guitars again.  It may be a few weeks before I can get back to all of you again.  I did play with the one that is still in my possession, and it seems better to me after moving the bridge back a bit.  I will have some friends check it out for me again to make sure.  Thanks again guys.

 

Douglas

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Permalink Reply by Hippy Chip on September 16, 2011 at 5:48pm

 first a question.  why such a short scale?

strings are manufactured for 24-26 inch scale.

if you get out of this range then string tension could be messing with 

your tuning.

as far as intonation goes I have 15 guitars in my collection right now.

12 of these I built myself. On all of them I set the bridge with string breakover point at 12th fret times 2 (within 1/16")

I checked the intonation with my electronic keyboard and they are dead on 

all the way to the 24th fret. 

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